The present invention relates to a device for adjusting thread tension and a thread drawing amount in a sewing machine.
An operator of the sewing machine normally adjusts an upper thread tension device with reference to the data of sewing conditions such as fabric sorts, thread sorts, stitching patterns, needle amplitude amount, fabric feed amount, etc., in order to position crossing points of an upper thread and a lower thread in a center of a fabric being stitched.
However, when the upper thread tension device is adjusted in response to the stitching conditions, for example, when the thread is tightened for a thick fabric or when a measure is prepared for shrinkages of the fabric in the thin fabrics or a pattern stitching with a large width such as zigzag stitching, the lower thread should be adjusted in addition to and in compliance with the adjustment of the upper thread. But satisfied stitches could not be produced with the adjustment of the upper thread only.